Someone who is so embittered and angry at life that they decided to flout the joyous camaraderie of geekdom at venues such as anime conventions or comicon by being a complete asshole to people by rejecting and disdaining fun and jovial gestures.

Con-goer: High five!
Con cunt: Fuck you.
Con-goer: (sarcastically, but not fully grasping the sincerity of the offense) Whoa, dude.